Filtration in hybrid inflators

ABSTRACT

An apparatus and method suitable for use in inflating a vehicle occupant restraint are provided. The apparatus stores a gas generating material in a first chamber and stores a supply of gas under pressure in a second chamber. When ignited, the gas generating material produces a hot gas which contains particulate material. To effect particulate removal, housed within the container and extending about the gas exit nozzle of the first chamber is a filter structure. The filter structure forms inner and outer mixing zones within the second chamber wherein portions of the stored gas mix with the appropriately generated and/or treated gas, forming inflation gas. The inflation gas in turn is passed through a diffuser and into the vehicle occupant restraint.

BACKGROUND OF THE INVENTION

This invention relates generally to inflatable restraint systems and,more particularly, to the type of inflator known as a hybrid inflatorand the treatment of gases therein.

Many types of inflators have been disclosed in the art for inflating anair bag for use in an inflatable restraint system. One type involves theutilization of a quantity of stored compressed gas which is selectivelyreleased to inflate the air bag. Another type derives a gas source froma combustible gas generating material which, upon ignition, generates aquantity of gas sufficient to inflate the air bag. In a third type, theair bag inflating gas results from the combination of a storedcompressed gas and the combustion products of a gas generating material.The last mentioned type is commonly referred to as an augmented gas orhybrid inflator.

Hybrid inflators that have been proposed heretofore have, in general,been subject to certain disadvantages. For example, the burning of thepyrotechnic (gas generating) and initiation materials in such inflatorsinvariably results in the production of particulate material. The use ofsuch a particulate-containing inflator emission to inflate an air bagcan in turn result in the particulate material being vented out from theair bag and into the vehicle.

Typically, the particulate material is variously sized and includes alarge amount of particulate within the respirable range for humans.Thus, the passage of the gas borne particulate material into thepassenger compartment of the vehicle, such as via conventional air bagventing, can result in the undesired respiration of such particulatematerial by the driver and/or other passengers which in turn can causeconsequent respiratory problems. Also, such particulate can easilybecome dispersed and airborne so as to appear to be smoke and therebyresult in the false impression that there is a fire in or about thevehicle.

It has also been proposed to screen the gaseous emission coming from thepyrotechnic portion of such hybrid inflators. For example, theabove-identified U.S. Pat. No. 5,131,680 discloses the inclusion of acircular screen "128" between the body of pyrotechnic material and theorifice through which the pyrotechnically produced emission is passed tothe pressurized gas-containing chamber of the hybrid inflator.

Also, U.S. Pat. No. 5,016,914 discloses the inclusion of a metal diskhaving a plurality of suitably sized openings therein. The disk isdisclosed as functioning to trap large particles such as may be presentin the generated gas.

Such techniques of filtering or screening the gaseous emission of thepyrotechnic section of the hybrid inflator prior to contact with thestored, pressurized gas of the inflator generally suffer such as fromundesirably slowing or preventing the transfer of heat to the stored gasfrom the relatively hot generated gas and particulate material. Ingeneral, such a transfer of heat to the stored gas is desired in hybridinflators in order to produce desired expansion of the gas.Consequently, the slowing or preventing of desired heat transfer canresult in a reduction in the performance of the inflator. Also, thescreening or filtering of particulate at this location within theinflator can undesirably effect gas flow within the inflator. Forexample, such treatment can undesirably restrict the flow of gas out ofthe pyrotechnic chamber, causing the pressure inside the pyrotechnicchamber to increase and thereby increase the potential for structuralfailure by the pyrotechnic chamber.

The above-identified U.S. Pat. No. 5,016,914 also discloses constraininggas flow to a tortuous path whereby additional quantities of relativelylarge particles produced by combustion of the gas generating materialare separated from the commingled gases as the gases flow toward theinflatable vehicle occupant restraint. As disclosed, various componentparts of the vehicle occupant restraint system cooperate to form thedescribed tortuous path. These component parts include the openings inthe container which direct the gas into an outer cylindrical diffuser,the container itself which preferably contains gas directing bladespositioned therein as well as burst disks to control the flow of the gasgenerated by ignition of the gas generating material. The patent alsodiscloses that in a preferred embodiment, a coating material, e.g., asilicone grease, is coated onto the inner surface of the container toassist in the fusing of particles thereto rather than allowing theparticles to rebound into the nitrogen gas jet stream.

Such surface coatings, however, generally suffer in several significantaspects with respect to effectiveness and functioning when compared, forexample, to the use of a filter to effect particulate removal.

First, as the nature of such fusion or adhesion of particles onto acoating is a surface phenomenon, the effectiveness of such removal isdirectly related to the amount of available surface area. In practice,such a surface coating provides a relatively limited amount of contactsurface area and, further, the effectiveness of such surface treatmenttypically is decreased as the available surface area is occupied.

Also, though such an internal surface coating may be of some use in thefusing of solid particles, such a coating would normally be relativelyineffective in trapping liquid phase particles. Furthermore, the processof condensation of liquid phase particles in an inflator normallyinvolves a transfer of heat to the subject contact surface. In the caseof such a surface coated with such a grease, such a transfer of heatcould undesirably result in the off-gassing of the coating material,e.g., production of gaseous byproducts of the coating material, which inturn would undesirably contribute to the toxicity of the gases emittedfrom such an inflator.

In addition, the effect of the flow of gases within the inflator canraise concerns about the use of inflators which utilize such coatings.For example, the impingement onto such a coating of the hot combustiongases produced within an inflator would normally tend to displace thecoating material, particularly since such coatings tend to become softerat elevated temperatures.

Thus, even for the short time periods associated with the operation ofsuch devices neither exclusive nor primary reliance is made by thispatent on the use of such a coating to effect particle removal.

There is a need and a demand for improvement in hybrid inflators to theend of preventing, minimizing or reducing the passage of particulatematerial therefrom without undesirably slowing or preventing heattransfer to the stored, compressed gas while facilitating proper bagdeployment, in a safe, effective and economical manner.

The present invention was devised to help fill the gap that has existedin the art in these respects.

SUMMARY OF THE INVENTION

A general object of the invention is to provide an improved inflatorapparatus suitable for use in inflating a vehicle occupant restraint.

A more specific objective of the invention is to overcome one or more ofthe problems described above.

The general object of the invention can be attained, at least in part,through an apparatus suitable for use in inflating a vehicle occupantrestraint that includes a container having a first chamber for storing agas generating material and a second chamber for storing a supply of gasunder pressure. The gas generating material when ignited generates a hotgas which contains particulate of the gas generating material andbyproducts thereof. The generated hot gas is releasable from the firstchamber into the second chamber by means of at least one gas exitnozzle.

The apparatus also includes a structure formed of at least one filtermaterial housed in the container and extending into the second chamberabout the gas exit nozzle of the first chamber. The filter structuredefines an inner mixing zone in the second chamber for mixing at least aportion of the particulate-containing generated hot gas with at least aportion of the stored gas to form a gas mix. The filter structure iscontacted by a gas comprising at least a portion of theparticulate-containing generated hot gas and effects reduction in theparticulate content of the contacting gas. The filter structure furtherdefines an outer mixing zone in the second chamber wherein an inflationgas for use in inflating the vehicle occupant restraint and comprising amix of gas of reduced particulate content and stored gas is formed.

The apparatus further includes a diffuser having at least onecontrolling orifice for providing passage therein of at least a portionof the inflation gas from the container. The diffuser also includes atleast one exit port for dispensing at least a portion of the inflationgas passing therein into the vehicle occupant restraint.

The prior art fails to adequately filter particulate from the gases ofhybrid inflator devices. For example, prior art techniques of filteringor screening the gaseous emission of the pyrotechnic section of thehybrid inflator prior to contact with the stored, pressurized gas of theinflator generally suffer such as from undesirably slowing or preventingthe transfer of heat to the stored gas.

The invention further comprehends a hybrid inflator for a vehicleoccupant restraint. The hybrid inflator includes an elongatedcylindrical container having a first chamber for storing a gasgenerating material and a second chamber for storing a supply of gasunder pressure. The gas generating material when ignited generates a hotgas that contains particulate of the gas generating material andbyproducts thereof. The particulate-containing generated hot gas isreleasable from the first chamber into the second chamber by means of agas exit nozzle at a first end on a first end portion of the firstchamber, with the gas exit nozzle being opposite a first inner end ofthe second chamber. A distance D separates the first end of the firstchamber from the first inner end of the second chamber.

This hybrid inflator also includes a structure formed of at least onefilter material housed in the container and extending into the secondchamber about the gas exit nozzle of the first chamber a distance L fromthe first end of the first chamber toward the first inner end of thesecond chamber. The filter structure is secured about the first endportion of the first chamber and defines an inner mixing zone in thesecond chamber for mixing at least a portion of theparticulate-containing hot generated gas with at least a portion of thestored gas to form a gas mix. The filter structure is contacted by a gascomprising at least a portion of the particulate-containing generatedhot gas and effects significant reduction in the particulate content ofthe contacting gas. The filter structure further defines an outer mixingzone in the second chamber wherein an inflation gas for use in inflatingthe vehicle occupant restraint and comprising a mix of gas of reducedparticulate content and stored gas is formed.

The hybrid inflator also includes a diffuser having at least onecontrolling orifice for providing passage therein of the inflation gasfrom the container and at least one exit port for dispensing theinflation gas into the vehicle occupant restraint.

The invention also comprehends a method for producing inflation gas inan apparatus suitable for use in inflating a vehicle occupant restraintand which includes a container having a first chamber for storing a gasgenerating material and a second chamber in which a supply of gas underpressure is stored. The method includes igniting the gas generatingmaterial stored in the first chamber to generate a hot gas whichcontains particulate of the gas generating material and byproductsthereof. The particulate-containing generated hot gas is released fromthe first chamber into the second chamber by means of at least one gasexit nozzle. The container houses a filter structure extending into thesecond chamber about the gas exit nozzle. The filter structure includesat least one filter material and defines an inner mixing zone and anouter mixing zone in the second chamber. At least a portion of theparticulate-containing generated hot gas is mixed with at least aportion of stored gas in the inner mixing zone to form a gas mix. Thefilter structure is contacted with a gas which includes at least aportion of the particulate-containing generated hot gas to effectsignificant reduction in the particulate content of the contacting gas.In the outer mixing zone, gas of reduced particulate content is mixedwith stored gas to form an inflation gas for use in inflating thevehicle occupant restraint. Such inflation gas is passed by means of adiffuser having at least one controlling orifice for providing passagetherein of at least a portion of the inflation gas and at least one exitport for dispensing at least a portion of the inflation gas passingtherein into the vehicle occupant restraint.

As used herein, the phrase "thrust neutral" refers to the production byan inflator of zero thrust when initiated as, for example, during adeployment event or accidentally during shipping, storage, or handlingthereof. That is to say, the gas discharge openings in the inflator areso positioned that the gas is discharged in opposing directions wherebythere are no resulting forces tending to cause physical movement of theinflator. Hence, the inflator will expend the energy generated thereby,generally in place.

The term "significantly reduced" and the like as used herein inreference to the particulate content of the gas or gases treated in thesubject invention (e.g., the hot gas released from the gas generatingmaterial storage chamber) means the removal of at least about 20% toabout 80% and generally the removal of at least about 50% of theairborne particulate from such a particulate-containing gas. Suchreduced particulate content gas can then be used in the formation ofinflation gas which satisfies the maximum allowable airborne particulatecontent for the inflation gas used in such inflatable restraint systems.

Other objects and advantages will be apparent to those skilled in theart from the following detailed description taken in conjunction withthe appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified, partially in section, schematic view of a hybridinflator in accordance with one embodiment of the invention.

FIG. 2 is a simplified, partially in section, schematic view of thehybrid inflator of FIG. 1 taken substantially along line 2--2 of FIG. 1and viewed in the direction of the arrows.

FIG. 3 is a fragmentary, sectional schematic view of the portion of thefilter structure shown in FIG. 2 encircled within A.

For ease of illustration and discussion, like parts in the drawings aredesignated by the same reference numeral.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an inflator, e.g., a hybrid inflator,having an internal filter structure useful in effecting removal, withinthe inflator, of particulate such as associated with the ignition andcombustion of gas generant materials used therein.

Referring to FIG. 1, a hybrid inflator assembly, generally designated10, for use in inflating a vehicle inflatable restraint cushion for thepassenger side of a vehicle is shown. While the invention will bedescribed below with reference to a passenger side assembly forautomotive vehicles including vans, pick-up trucks, and particularlyautomobiles, it is to be understood that the invention also hasapplicability with other types or kinds of such assemblies includingdriver side assemblies.

With respect to such automotive vehicles it will be appreciated that dueto usual physical differences between passenger and driver sideassemblies, e.g., passenger side air bags generally are comparativelylarger than those used in driver side assemblies and thus such passengerside assemblies typically require a comparatively larger volume ofinflating gas, the invention has particular utility in passenger sideassemblies.

As shown in FIG. 1, the inflator assembly 10 includes an elongated,generally cylindrically shaped pressure vessel or container 12. It willbe appreciated, however, that if desired variously sized and shapedcontainers including, for example, those having a cylindrical, toroidal,spherical or selected intermediary shape can be used in the practice ofthe invention.

The container 12 includes a storage chamber 14 useful in effecting gasredirection and for use in storing a supply of gas under pressure. Forexample, as described above, an inert gas such as argon or nitrogen at apressure typically in the range of 2000-4000 psi can be used to fill andpressurize the storage chamber 14. It is to be understood, however, thatthe chamber 14 could be used to store other selected gases (e.g., carbondioxide, air, other inert gases or one or more combinations of suchgases) and/or gases at other storage pressures, as desired.

The chamber 14 is defined by an elongated cylindrical sleeve 16. An endplug 20 is attached by means of a circumferential weld 22 in sealingrelation to a first end 24 of the sleeve 16. The end plug 20 includes apassage (not shown) through which the gas to be stored can be conductedinto the chamber 14. Once the chamber 14 has been filled with gas at thedesired pressure, the passage is closed. The end plug 20, eitherseparately or as an integral part thereof, includes a conventionalpressure switch (not shown), commonly referred to as a low pressuresensor ("LPS"), from which gas pressure in the chamber 14 can bemonitored to alert the vehicle occupant should the pressure in thechamber 14 drop below a predetermined pressure.

A gas generator housing 30 is recessed in sealing relation into thechamber 14 from a second end 32 of the sleeve 16, with a collar 34 aboutthe mid-section of the gas generator housing 30 being attached by meansof a circumferential weld 36 with the sleeve 16.

The gas generator housing 30 includes a chamber 40 for use in storingtherein a supply of gas generating material, e.g., a pyrotechnic chargesuch as a granular mixture of BKNO₃ or extrudable solid propellants suchas combinations of binders, used as a fuel, with solid oxidizers such asa combination of polyvinyl chloride (fuel) with potassium nitrate orpotassium perchlorate (oxidizer), for example.

The chamber 40 includes an end portion 41 forming an inner end 42 havinga central opening or nozzle orifice 44 wherethrough hot gas generatedupon ignition of the gas generating material is released into thechamber 14. It is to be understood, however, that the number,positioning and shape of such nozzle orifice or orifices can beappropriately altered to satisfy design requirements for particularinstallations as will be apparent to those skilled in the art.

The hot gas typically contains particulate of the gas generatingmaterial and byproducts thereof. The nature of such particulate materialwill at least in part be dependent on the nature of the gas generatingmaterial itself. Thus, for BKNO₃, typical particulate is in the natureof boron and/or potassium compounds.

Housed in the container 12 and extending into the chamber 14 about saidgas exit nozzle 44 of the chamber 40 is a structure 50 composed of afilter material 51 having an inner surface 52 and an outer surface 53.The filter structure 50 is generally cylindrical in shape and extendsfrom the gas generator housing 30 towards the end plug 20. The filterstructure 50 defines within the chamber 14 both an inner and an outermixing zone, respectively designated by the reference numerals 54 and56. A first end portion 60 of the filter structure 50 is spot welded tothe gas generator 30, such as about the end portion 41. It will beunderstood that other means of appropriately positioning and placing thefilter structure 50 within the inflator assembly 10 can, if desired, beutilized without departing from the subject of the invention.

In the illustrated embodiment, a distance D separates the gas generatorhousing, i.e., the end 42, from the inner end 61 of the end plug 20while the filter structure 50 is shown as extending a distance L fromthe gas generator housing 30, i.e., again the end 42, towards the endplug 20, with L being less than D such that a second end portion 62 ofthe filter structure is free standing within the chamber 14. In aninflator assembly so dimensioned, it will be appreciated that a portionof the hot gas exiting from gas generator housing 30 can pass throughthe filter material 51, such as shown by the arrows 64, for example, orcan pass through the interior of the filter structure 50 and exit from asecond end portion 62 thereof, such as shown by the arrows 66.

It is to be understood, however, that the length of the filter structureof the invention can, if desired, be appropriately varied and/ormodified dependent on the specifics of a particular installation. Forexample, the filter structure can be made to extend substantially to theend of the inflator, e.g., such that L substantially equals D or thestructure of the filter can be modified such that the second end portion62 does not permit gas to pass therethrough without passing through thefilter material 51, e.g., the second end portion can be drawn togetheror otherwise closed off (not shown) with filter material.

Also, if desired, the filter structure 50 can be selectively supportedor fastened with other portions of the inflator assembly along thelength thereof. For example, if desired, the second end portion 62 canbe fastened such as by a bracket (not shown) with the end plug 20.

In the inner mixing zone 54, the particulate-containing generated hotgas formed upon the ignition and combustion of the gas generant materialand which has exited from the chamber 40 into the chamber 14 is mixedwith at least a portion of the stored gas therein to form a gas mix.Such dispersing of the hot gas results in both a slowing and a coolingthereof, as compared to when such gas is first released from the chamber40 through the gas exit nozzle 44. Thus, such an inner mixing zonepermits the slowing and cooling of the gas prior to contact with thefilter structure which in turn permits the utilization of various filtermaterials which ordinarily would not be able to effectively withstandthe gas velocities and temperatures normally associated with suchgenerated gases upon release from such a pyrotechnic chamber.

The filter structure 50 by way of the filter material 51 effects removalof at least a portion of the particulate in the particulate-containinggas contacting therewith, e.g., the particulate-containing generated hotgas and/or other gas which includes at least a portion of particulatefrom the particulate-containing generated hot gas, such as the gas mixformed in the inner mixing zone 54 or the gas mix formed in the outermixing zone 56, for example. As a result, a gas having a reducedparticulate content is formed. It will generally be preferred that suchparticulate removal result in significant reduction in the particulatecontent of the gas so treated, e.g., the removal of at least about 20%to about 80% and generally the removal of at least about 50% of theairborne particulate from the particulate-containing generated hot gas.

In practice, such particulate removal is generally in the nature ofcondensation of liquid phase particulate and/or entrapment ofparticulate onto the filter material 51. It is theorized thatcondensation of particulate, wherein heat removal results in a phasechange and resultant condensation of particulate on available filtersurface area, is facilitated when the particulate-containing gas beingfiltered contacts the filter structure 51 at lower velocity. Thus, gasslowing and cooling such as may be realized as a result of the gasdispersing resulting from the mixing of generated gas with stored gaswithin the inner mixing zone can contribute to the effectiveness of thefilter structure in the removal of particulate from the gas prior toemission from the inflator. Additional particulate removal is believedeffected by means of particulate entrapment within the filter material51 whereby particulate (solid) is physically separated from the medium(gas).

It is believed that particulate removal, such as by particulatecondensation, is effected by contact of particulate-containing gas ontothe filter structure and is not limited to removal of particulate fromthat portion of the gas which passes through the filter material. It isthus believed that particulate can be removed from the gas as suchparticulate-containing gas contacts either the inner surface 52 or theouter surface 53 of the filter material 51.

In view thereof, the filter material 51 of the filter structure 50desirably provides sufficient surface area to effect desired particulatecondensation and/or provide sufficient porosity and tortuous flow pathto effect desired particulate entrapment. Thus, the filter structure 50serves to reduce the amount of particulate expelled from the hybridinflator 10. As a result, inflator emission toxicity and particulatelimits can be desirably satisfied.

In the outer mixing zone 56, the stored gas within the zone 56 is mixedwith the gas of reduced particulate content to form an inflation gas foruse in inflating the vehicle occupant restraint. It will also beappreciated that a portion of the particulate-containing generated hotgas may, as shown in FIG. 1 by the arrows 66, exit through the endportion 62 of the filter structure 50 and also mix with the gas storedwithin the zone 56 and/or gas of reduced particulate content. The amountor proportion of gas so passing can be appropriately limited orcontrolled, as desired, to result in the desired particulate content inthe gas emitted from the inflator, as will be appreciated by one skilledin the art and guided by the teachings herein provided.

Reference is now made to FIGS. 2 and 3 wherein the filter structure 50is shown in greater detail. As shown in FIG. 3, the filter material 51used in the formation of the structure 50 includes an outer and an innerfine metal wire screen or expanded metal layers, respectively designated70 and 72, with a filter element layer 74, such as of ceramic paper ortextile, therebetween.

It is to be understood that the filter structure of the invention can becomposed of one or more of a number of filter materials. In fact, thepractice of the invention facilitates the effective use of a relativelywide variety of filter materials or mediums in the filter structure ofthe invention. For example, the filter structure can, if desired, becomposed of one or a combination of filter materials including: ceramicpaper such as LYTHERM (a trademark of Lydall Inc.) having a permeabilityof 30-200 cfm/sq ft at 1/2" water pressure drop, ceramic textile such asKAO-TEX (a trademark of Thermal Ceramics Inc.) or NEXTEL (a trademark of3M), woven stainless steel wire such as by National Standard Co. andtypically having an open area in the range of about 20 to 60 percent,such as a fine wire screen such as a single wrap of 45×170 meshstainless steel Dutch weave or two to three wraps of 30×30, 50×50, or100×100 mesh stainless steel screen or expanded metal, such as expandedstainless steel, also having an open area in the range of about 20 to 60percent.

In general, such ceramic papers and textiles, if used, are used incombination with one or more support layers of such a woven or expandedmetal material. For example, such a multi-part filter body can have asandwich-like form, such as shown in FIG. 3, wherein a filter elementsuch as ceramic paper or ceramic textile is sandwiched between an outerand an inner support layer such as of the above-identified woven 50×50or 30×30 stainless steel.

In the embodiment illustrated in FIG. 1, the gas generator housing 30includes an inflator diffuser 80, adjacent to and integral with thepyrotechnic chamber 40. That is, the diffuser 80 comprises a generallycylindrical sleeve 82 that is joined at a first end 84 to thepyrotechnic storage chamber 40. An opposite second end 86 of thediffuser 80 extends external the container 12. Generally equally spacedcontrolling orifices 90 are positioned about the cylindrical sleeve 82,adjacent the first end 84. The controlling orifices 90 provide passageinto the diffuser 80 of inflation gas from the container 12. Thisinflation gas can then exit the inflation apparatus, i.e., the inflatorapparatus 10, by means of gas exit ports 92 spaced about adjacent thesecond end 86 of the diffuser 80.

Oval shaped gas exit ports 92 are generally equally spaced about thecircumference of the diffuser end 86 so as to promote a more uniformdistribution of the exiting gas about the circumference of the inflatorassembly 10 and to desirably result in the assembly being thrustneutral. It is to be understood, however, that the number, spacing, andshaping of the gas exit ports can be appropriately altered to satisfydesign requirements for particular installations as will be apparent tothose skilled in the art.

In the illustrated embodiment, the gas exit nozzle 44 is generallysituated in a fashion such that the nozzle 44 is centered towards oneend of the filter structure 50 along the central longitudinal axis 94thereof. It will be appreciated that the gas initially exiting from thepyrotechnic chamber 40 through the gas exit nozzle 44 will be initiallygenerally directed through the inner mixing zone 54 of the filterstructure 50 towards the end plug 20. Thus, upon exiting from thepyrotechnic chamber 40, the generated gas will commingle with stored gaswithin the inner mixing zone 54.

It will be appreciated that while in the embodiment illustrated in FIG.1 the gas initially exiting from the pyrotechnic chamber 40 will beinitially generally directed towards the end plug 20, the controllingorifices 90 whereby gas exits from the chamber 14 is positioned near oradjacent the end 32 opposite thereto. Thus, the gas released from thechamber 40 will undergo at least an approximately 180° cumulative changein direction between its release into the chamber 14 and subsequentpassage through the diffuser 80.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations are to be understoodtherefrom, as modifications within the scope of the invention will beobvious to those skilled in the art.

What is claimed is:
 1. An apparatus suitable for use in inflating avehicle occupant restraint comprising:a container having a first chamberfor storing a gas generating material and a second chamber for storing asupply of gas under pressure, the gas generating material when ignitedgenerating a hot gas, the generated hot gas containing particulate ofthe gas generating material and byproducts thereof and being releasablefrom said first chamber into said second chamber by means of at leastone gas exit nozzle; a structure comprising at least one filter materialhoused in said container and extending into said second chamber aboutthe gas exit nozzle of said first chamber, said filter structuredefining an inner mixing zone in said second chamber for mixing at leasta portion of the particulate-containing generated hot gas with at leasta portion of the stored gas to form a gas mix, said filter structurebeing contacted by a gas comprising at least a portion of theparticulate-containing generated hot gas and effecting reduction in theparticulate content of the contacting gas, said filter structure furtherdefining an outer mixing zone in said second chamber wherein aninflation gas for use in inflating the vehicle occupant restraint andcomprising a mix of gas of reduced particulate content and stored gas isformed; and a diffuser having at least one controlling orifice forproviding passage therein of the inflation gas from said container andat least one exit port for dispensing the inflation gas into the vehicleoccupant restraint.
 2. The apparatus of claim 1 wherein said filterstructure comprises an inner and an outer surface and said reduction inparticulate content comprises particulate condensation on said innersurface and particulate entrapment in said filter material as at least aportion of the particulate-containing generated hot gas passestherethrough upon contact therewith.
 3. The apparatus of claim 2 whereinsaid reduction in particulate content comprises significant reduction inparticulate content.
 4. The apparatus of claim 3 wherein said reductionin particulate content additionally comprises particulate condensationon said outer surface.
 5. The apparatus of claim 1 wherein there is atleast an approximately 180° cumulative change in gas direction betweenthe release of the particulate-containing generated hot gas from saidfirst chamber and the passage of the inflation gas into said diffuser.6. The apparatus of claim 1 wherein said filter structure comprises atleast one support layer of a woven stainless steel screen having an openarea in the range of about 20 to 60 percent.
 7. The apparatus of claim 6wherein said filter structure comprises both an outer and an innersupport layer and additionally comprises at least one layer of filterelement between.
 8. The apparatus of claim 6 wherein said filterstructure comprises both an outer and an inner support layer of a wovenstainless steel screen having an open area in the range of about 20 to60 percent and additionally comprises a layer of filter elementcomprising ceramic paper or ceramic textile therebetween.
 9. Theapparatus of claim 1 wherein:a) said gas exit nozzle is at a first endof a first end portion of said first chamber and is opposite a firstinner end of said second chamber, b) a distance D separates the firstend of said first chamber from the first inner end of said secondchamber, c) said filter structure comprises an elongated cylindricalshape with said filter structure extending a distance L from the firstend of said first chamber toward the first inner end of said secondchamber, and d) distance L is less than distance D.
 10. A hybridinflator for a vehicle occupant restraint, said hybrid inflatorcomprising:an elongated cylindrical container having a first chamber forstoring a gas generating material and a second chamber for storing asupply of gas under pressure, the gas generating material when ignitedgenerating a hot gas, the generated hot gas containing particulate ofthe gas generating material and byproducts thereof and being releasablefrom said first chamber into said second chamber by means of at leastone gas exit nozzle at a first end of a first end portion of said firstchamber with said gas exit nozzle being opposite a first inner end ofsaid second chamber, and wherein a distance D separates the first end ofsaid first chamber from the first inner end of said second chamber; anelongated cylindrical structure comprising at least one filter materialhoused in said container and extending into said second chamber aboutsaid gas exit nozzle of said first chamber a distance L from the firstend of said first chamber toward the first inner end of said secondchamber, said filter structure being secured about said first endportion of said first chamber and defining an inner mixing zone in saidsecond chamber for mixing at least a portion of theparticulate-containing generated hot gas with at least a portion of thestored gas to form a gas mix, said filter structure being contacted by agas comprising at least a portion of the particulate-containinggenerated hot gas and effecting significant reduction in the particulatecontent of the contacting gas, said filter structure further defining anouter mixing zone in said second chamber wherein an inflation gas foruse in inflating the vehicle occupant restraint and comprising a mix ofgas of reduced particulate content and stored gas is formed; and adiffuser having at least one controlling orifice for providing passagetherein of the inflation gas from said container and at least one exitport for dispensing the inflation gas into the vehicle occupantrestraint.
 11. The hybrid inflator of claim 10 wherein distance L issubstantially the same as distance D.
 12. The hybrid inflator of claim10 wherein distance L is less than distance D.
 13. The hybrid inflatorof claim 12 wherein a first end of the filter structure is secured aboutthe first end portion of said first chamber and an opposite second endof the filter structure is free standing within said second chamber. 14.The apparatus of claim 10 wherein said filter structure comprises atleast one support layer of a woven stainless steel screen having an openarea in the range of about 20 to 60 percent.
 15. The apparatus of claim14 wherein said filter structure comprises both an outer and an innersupport layer and additionally comprises at least one layer of filterelement between.
 16. The apparatus of claim 14 wherein said filterstructure comprises both an outer and an inner support layer of a wovenstainless steel screen having an open area in the range of about 20 to60 percent and additionally comprises a layer of filter elementcomprising ceramic paper or ceramic textile therebetween.
 17. A methodfor producing inflation gas in an apparatus suitable for use ininflating a vehicle occupant restraint and comprising a container havinga first chamber for storing a gas generating material and a secondchamber in which a supply of gas under pressure is stored, said methodcomprising the steps of:igniting the gas generating material stored inthe first chamber to generate a hot gas, the generated hot gascontaining particulate of the gas generating material and byproductsthereof, releasing the particulate-containing generated hot gas from thefirst chamber into the second chamber by means of at least one gas exitnozzle, the container housing a structure comprising at least one filtermaterial extending into the second chamber about said gas exit nozzle,the filter structure defining an inner mixing zone and an outer mixingzone in the second chamber, mixing at least a portion of theparticulate-containing generated hot gas with at least a portion of thestored gas in the inner mixing zone to form a gas mix, contacting thefilter structure with a gas comprising at least a portion of theparticulate-containing generated hot gas to effect significant reductionin the particulate content of the contacting gas, mixing gas of reducedparticulate content and stored gas in the outer mixing zone to form aninflation gas for use in inflating the vehicle occupant restraint, andpassing the inflation gas by means of a diffuser having at least onecontrolling orifice for providing passage therein of at least a portionof the inflation gas and at least one exit port for dispensing at leasta portion of the inflation gas passing therein into the vehicle occupantrestraint.
 18. The method for producing inflation gas of claim 17wherein the filter structure has an inner and an outer surface and saidcontacting step comprises contacting the inner surface with at least aportion of the gas comprising the particulate-containing generated hotgas to effect particulate condensation on the inner surface of thefilter structure and particulate entrapment in said filter material asat least a portion of the particulate-containing generated hot gaspasses therethrough upon contact therewith.
 19. The method for producinginflation gas of claim 18 wherein said contacting step additionallycomprises contacting the outer surface of the filter structure with atleast a portion of the gas comprising the particulate-containinggenerated hot gas to effect particulate condensation on the outersurface of the filter structure.
 20. The method for producing inflationgas of claim 18 wherein there is at least an approximately 180°cumulative change in gas direction between the releasing of theparticulate-containing generated hot gas from said first chamber and thepassing of the inflation gas into said diffuser.